Tritiated ATP has been used as an essential component of several studies at the NTLF over the past few years. In initial studies [2-3H]-ATP of high specific activity was synthesized from 2-Bromo-ATP by heterogeneous tritiodehalogenation using tritium gas and PdO in aqueous solution. Availability of this labelled material allowed development of an enzymatic synthesis of highly tritiated RNA. This overall approach will be repeated and improved. Similar chemistry was used recently to facilitate the production of [2-3H]-Deoxyadenosine for derivatization to the phosphoramidite, and subsequent incorporation into a DNA fragment. This overall process will also be repeated and improved. A particular improvement may involve moving away from chemical synthesis, and we will pursue the enzymatic synthesis of tritiated DNA by incorporation of tritiated dATP. To aid this approach we have mebarked on a large scale synthesis of 2-Br-dATP to be used in an analogous tritiation reaction to 2-Br-ATP for RNA synthesis. The ability to synthesize specifically labelled RNA and DNA molecules will allow some very specific macromolecular NMR experiments to be conducted, addressing the interactions between DNA, proteins, RNA and other ligands.